Collapsible screw-threading tap.



H. AUSTIN.- COLL APSIBLE SCREW THREADING TAP.

. APPLICATION l'ILED AUG.21, 1916. 1,234,,602w Patented July 24,1917.

' 2 SHEETSSHEET 1.

H. AUSTIN.

COLLAPSIBLE SCREW THREADING TAP.

Patented July 24, 1917.

APPLICATION FILED AUG.2I,1916.

2 SHEETSSHEET 2 HERBERT AUSTIN", OF BROMSGROVE, ENGLAND.

: COLLAPSIBLE SCBEW-THREADING TAP.

Application filed August 21, 1916.

To all whom it may concern:

Be it known that I, HERBERT A s'rIN, a subject of the King of GreatBritain, and residing at Bromsgrove, in the county of Worcester,England, engineer, have invented certain new and useful Improvements inCollapsible Screw-Threading Taps, of which the following is aspecification.

This invention relates to the type of collapsible tap, for use in theformation of screw-threads, in which dies for cutting the threads arecarried by a stock and are moved outward against the force of a springor springs by means of a central bolt or plug which is moved for thepurpose axially of the tap. In this type of collapsible tap, aspreviously proposed, it has been necessary for the bolt to be movedbackward a considerable distance, in relation to the dies, to enable thetap to be withdrawn from the work.

Now, this invention has for its objects to improve the construction ofthe tap with a view to insuring that quite a small backward movement ofthe bolt or plug in relation to the dies will enable them to move fullyinward, and further to improve the construction of the tap.

Convenient practical forms of the invention are illustrated by thedrawings herewith, of which 2- Figure 1 shows, mainly in longitudinalsection, a form of the invention especially applicable to a smaller sizeof tap.

Fig. 2 is a side view of the tap shown by Fig. 1, looking in thedirection of the arrow.

Fig. 3 is a section taken in the plane indicated by line 3-3 of Fig. 1.

Fig. 1 shows, in longitudinal section, a form of the invention speciallyapplicable to a larger size of tap.

Fig. 5 is a half section taken in the plane indicated by line 5-5 ofFig. 4.

Fig. 6 is a side view of the tappet and a section of the lever handleused with the tap shown by Figs. 4 and 5; and,

Fig. 7 is a View illustrating a modified arrangement of collars of thebolt or plug.

Referring first to Figs. 1, 2 and 3 :A is the stock of the cap, 13 areradial dies of which the cutting surfaces project through slots at whichare formed in from the forward end of the stock. G is a cap which isfixed by screws such as 0 against the outer end of the stock to closethe slots a and prevent the dies moving endwise of the tap.

Specification of Letters Patent.

Patented July 24:, 1917.

Serial No. 116,012.

D is a plug which is formed with a number of collars d and passesaxially through a chamber a of the stock and is guided at its rear endthrough an opening a at the inner end of the chamber, and at its outerend, where it is reduced in diameter, is guided through an adjusting nutE. The inner ends or bases of the dies 13 are formed as segments 6 of anannulus, and these bases are situated within the outer portion of thechamber a. Springs F are arranged within holes a of the stock A and abutat their outer ends against plugs f which are screwed into the outerends of the holes, and abut at their inner ends each partially againstone of the bases 7) and partly against the adj acent base, and thediesare constantly pressed in an inward direction by the springs F. Thecollars cl around the plug D are each formed with a beveled surface clat the forward end, and the .peripheral surface may be cylindrical, orpreferably somewhat tapered, as shown, in either of which cases thethrust of the dies thereagainst will not force back the plug D. Theinner surfaces of the bases of the dies are formed with projections b,of which the sides are beveled to correspond with the beveled surfacesd, and of which the faces immediately forward of the beveled surfacesare cylindrical, or somewhat tapered, to correspond with the peripheralsurfaces of the collars (Z. In Fig. 1 the peripheral surfaces of thecollars (Z are shown as passing across the peripheral surfaces of theprojections 6, thus holding out the dies B in their operative positions.When the plug D is drawn back the periph eral surfaces (Z pass clearfrom the corresponding surfaces of the projections Z) and the springs Fmove in the dies and allow the tap to be withdrawn from a hole withinwhich it has cut a screw-thread, the projections 7) passing into thespaces between the collars. lVhen the plug is again advanced the beveledsurfaces d engage with the beveled surfaces 6 and move out the dies, andby further advancing the plug the peripheral surfaces (Z again engagewith the corresponding surfaces of the projections Z) and maintain thedies in their outward positions. G is a lever which may be formed with ahandle on its outer end. This lever passes through a. slot a of thestock and engages with a slot (Z which is formed through the rear end ofthe plug D, and the lever is pivoted to the outer end of an inclinedstud H which is secured at its inner end within the stock A. The plugmay thus be drawn backward and may, if desired, be moved forward also,by hand, but to render the backward movement of the plug D auto matic, atappet J is slidably mounted in a lug a of the stock, so that when theforward end of the tappet comes against an outer face of the articlewhich is being operated upon by the tap it will be moved backward inrelation to the tap and by pressing against the lever G will move suchlever back and consequently the plug. By arranging the tappet to pressagainst the lever near to the fulcrum thereof, a very short movement ofthe stock, after the tappet has come against an obstruction, causes theplug to move back the necessary distance. A wearing piece j may be letinto the forward end of the tappet. The tappet may be arranged to comeagainst any fixed abutment, in lieu of coming against a face of thearticle which is be ing operated upon. A spiral spring M is shown assurrounding the plug D and abutting at its rear end against a shoulderof the interior of the stock and at its forward end against a collar (Zof the plug, the purpose of this spring being to insure that when theplug has been moved into position in which it holds out the dies intheir operative positions it cannot. accidentally move back, the spring,however, being of such strength only that when the plug has been movedback the spring cannot move it forward again sui'ii ciently to move outthe dies. As already de scribed, it is preferred to make the peripheralsurfaces of the collars (Z and the corresponding surfaces of theprojections Z) somewhat taper, as shown, the purpose of this being toenable the degree to which the dies are moved out to be readily adjustedby adjusting the distance to which the plug can be moved in a forwarddirection. When the plug is in its forward position, a'shoulder thereofcomes against the inner face of the nut E, and therefore the point towhich the plug can be moved forward may be readily adjusted by screwingup or unscrewing the nut.

For convenience and accuracy of manufacture, it is preferred to form allthe peripheral surfaces of the collars (Z and the corresponding surfacesof the projections 12 as surfaces of a common cone; and for the samereason it is preferred to form the dies together in one piece with anannulus and subsequently divide the annulus through to form the separatedies with their bases.

Referring now to Figs. 4, 5 and 6 :The tap illustrated thereby issubstantially the same as that shown by Figs. 1, 2 and 3, but variessomewhat in detail. The parts shown in Figs. 4, 5 and 6 which correspondto those shown by Figs. 1, 2 and 3, are similarly lettered. A rod Npasses through an axial hole of the plug D. This rod has portions 7?. nof reduced diameter having screwed on their outer ends, respectively,pairs of locknuts n a The portion of larger diameter of this rod enterssome distance into the rear end ofthe plug. A lever G, which may beformed with a handle at its outer end, is pivoted within a slot a whichis formed through the side of the stock A, and the inner end of thislever passing through a slot d of the plug engages with a slot a whichis formed through'the portion of enlarged diameter of the'rod N. Theplug D is moved forward by the lever G pressing the forward end of theportion of enlarged diameter of the rod N against a shoulder (i of theinterior of the plug, and is moved back again by the lever drawing backthe rod N and causing the lock-nuts n to carry back the plug. P is adouble-armed tappet which is carried by a stud Q. which is fixed to thestock. then the plug D has been moved forward and is holding out thedies B, the arm 7) of the tappet P is engaged with a shoulder g of thelever G and prevents the lever from being moved in a direction to moveback the plug, and the other arm p of the tappet stands outward in adirection approximately at right-angles to the axis of the tap. The arm7) has an adjusting screw screwed therethrough, and as the tap iscompleting an operation, the nose [9 of this screw comes in contact witha forward face 7* of an article R- which is being tapped (or it might bearranged to come in contact with a face of a fixed abutment) and movesthe arm 7) clear of the shoulder g of the lever G, whereupon a spiralspring S moves back the rod N and plug D. This spring S surrounds therearward part of the rod N and bears at its forward end against ashoulder a of the interior of the stock and at its rear end against acollar 8 which surrounds the rod and is prevented from moving rearwardin relation to the rod by the lock-nuts n and a washer s. The inner faceof the inner lock-nut n is, when the plug is in its forward positionagainst the inner face of the adjusting nut E, some little distance backfrom the outer end of the plug, with the result that when the spring Sbegins to act it first simply moves back the rod N until the innerlock-nut n comes against the outer end of the plug and then moves backthe plug also; otherwise there would be a tendency for the plug to stickand-not yield backward under the pull of the spring, whereas the initialmo-vement of the rod in a backward direction be- The cap C is shown inthis case as formed as a flange with a socket-piece 0 formed therewith,and in the forward edge of this socket-piece there are formed a numberof turrets 0 with any one of which a key 0 may be engaged and thensecured by a screw 6 to the nut E so as to prevent the nut from workingloose. Such an arrangement may be also employed in connection with thetap described with reference to- Figs. 1, 2 and 3, as will be obvious.

Referring now to Fig. 7 the collars d of the plug D are cylindrical andenlarge some what in diameter one behind the other, and an extra collar65* is provided which, when the dies B are worn or have become re-cut,may be brought into action by advancing the plug to such an extent thatthe leading collar becomes inoperative while the rearmost collar becomesoperative, the nut E being screwed forward as required to enable this tobe done.

Having fully described my invention, what I claim and desire to secureby Letters Patent is 1. In a collapsible tap for use in the formation ofscrew threads, the combination of a stock, dies which are slidablyfitted within said stock and are constantly pressed in an inwarddirection by means of a spring or springs, a central bolt or plug whichis movable endwise within said stock, collars around said bolt or plugwhich are spaced apart by a clearance groove or grooves, projections atthe inner ends of said dies which are also spaced apart by a groove orgrooves, said collars and said projections formed with beveled orcorresponding faces, of which those of the collars engage with those ofthe dies when the bolt or plug is moved endwise in one direction andthereby move out the dies against the force of a spring or springs, andsaid collars and projections formed, behind the said beveled or corresponding faces, respectively, with peripheral surfaces which arecomparatively sli htly tapered and engage with one another when the bolthas been moved in such direction and insure that the pressure of thedies against the collars will have no substantial tendency to move backthe bolt or plug, and means whereby the bolt or plug may be moved in theopposite direction, in relation to the stock, and allow the dies to movein, the projections of the inner ends of the dies then entering withinthe groove or grooves of the bolt or plug.

2. In a collapsible tap for use in the formation of screw-threads, thecombination of a stock, dies which are slidably fitted within said stockand are constantly pressed in an inward direction by means of a springor springs, a central bolt or plug which is movable endwise within saidstock, collars around said bolt or plug which are spaced apart by aclearance groove or grooves, proj ections at the inner ends of said dieswhich are also spaced apart by a groove or grooves, said collars andsaid projections formed with beveled or corresponding faces,respectively, of which those of the collars engage with those of thedies when the bolt or plug is moved endwise in one direction and therebymove out the dies against the force of a spring or springs and saidcollars and projections formed with tapered peripheral surfaces behindthe said beveled or corresponding faces, respectively, which are formedas surfaces of a common cone and engage with one another when the bolthas been moved in such direction and insure that the pressure of thedies against the collars will have no substantial tendency to move backthe bolt or plug, and means whereby the bolt or plug may be moved in theopposite direction, in relation to the stock, and allow the dies to movein, the projections of the inner ends of the dies then entering withinthe groove or grooves of said bolt or plug.

3. In a collapsible tap for use in the for mation of screw-threads, thecombination of a stock, a cap which is fixed to the forward end of thestock, dies which are slidably fitted within said stock and areconstantly pressed in an inward direction by a spring or springs, acentral bolt or plug which is movable endwise within said stock, collarsaround. said bolt or plug which are spaced apart by a clearance grooveor grooves, projections at the inner ends of said dies which are alsospaced apart by a groove or grooves, said collars and said projectionsformed with beveled or correspondin surfaces of which those of thecollars engage with those of the dies when the bolt or plug is movedendwise in one direction and thereby move out the dies against the forceof a spring or springs, a nut which is screwed into the said cap andforms a stop to the movement in said direction of the bolt or plug andmay be adjusted in relation to the cap to adjust the distance to whichthe bolt or plug may be moved in such direction, and means whereby thebolt or plug may be moved in the opposite direction, in relation to thestock, and allow the dies to move in, the projections of the inner endsof the dies then entering within the groove or grooves of the bolt orplu 4. In a collapsible tap for use in the formation of screw-threads,the combination of a stock, dies which are slidably fitted within saidstock and are constantly pressed in an inward direction by a spring orsprings, a central bolt or plug which is movable endwise within saidstock, collars around said bolt or plug which are spaced apart by aclearance groove or grooves, projections at the inner ends of said dieswhich are also spaced apart by a groove or grooves, said collars andsaid projections formed with beveled or corresponding surfaces of whichthose of the collars engage with those of the dies when the bolt or plugis moved endwise in one direction, and thereby move out the dies againstthe force of a spring or springs, a spring which constantly tends tomove such bolt or plug in the direction to move out the dies and insuresthat the bolt or plug cannot accidentally return afterit has been movedfully in such direction but is not of sufficient strength to cause thebolt or plug after it has been moved back to move forward againsufficiently to move out the dies, and means whereby the bolt or plugmay be moved back, in. relation to the stock, and allow the dies to movein, the projections of the inner ends of the dies then entering withinthe groove or grooves of the bolt or plug.

5. In a collapsible tap for use in the for mation of screw-threads, thecombination of a stock, dies which are slidably fitted within said stockand are constantly pressed in an inward direction by a spring orsprings, a central bolt or plug which is moved endwise within saidstock, collars around said bolt or plug which are spaced apart by aclearance groove or grooves, projections at the inner ends of said dieswhich are also spaced apart by a groove or grooves, said collars andsaid projections formed with beveled or corresponding surfaces of whichthose of the collars engage with those of the dies when the bolt or plugis moved endwise in one direction and thereby move out the dies againstthe force of the spring or springs, an axial rod which passes throughsaid bolt or plug, a shoulder of such rod which as the rod moves forwardcomes against a shoulder of said bolt or plug and moves said bolt orplug forward, a shoulder at the forward end of said rod which when theother shoulder is against the shoulder of the bolt or plug is somedistance forward of the forward end of the bolt or plug, a spring whichsurrounds said rod and tends constantly to move it backward, a leverwhich is carried by said stock and engages with said rod, and a tappetwhich is carried by said stock and retains said lever in positionholding the rod forward but on coming against an abutment releases saidlever and allows the spring to move the rod backward until the shoulderat the forward end thereof comes against the forward end of the bolt orplug when the further backward movement of the rod moves back also thebolt or plug andallows the projections of the inner ends of the dies toenter within the groove or grooves of the bolt or plug.

6. In a collapsible tap for use in the formation of screw-threads, thecombination of a stock, dies which are s'lidably fitted within saidstock and are constantly pressed in an inward direction by the spring orsprings, a central bolt or plug which is movable endwise within saidstock, collars around said bolt or plug having forward surfaces whichare beveled or correspOndinglyshaped, and

peripheral cylindrical surfaces behind the beveled orcorrespondingly-shaped surfaces, respectively, said collars enlarging indiameter one behind another, and spaced apart by a clearance groove orgrooves, corresponding projections at the inner ends of said dieswhichare also spaced apart by a groove or grooves, all the said collars,except the rearmost collar, engaging with the projections of the dieswhen the bolt or plug is moved endwise in one direction, thereby movingout the dies against the forceof the spring or springs, said rearmostcollar being operative only after the dies have become worn or have beenre-cut, the foremost collar being then inoperative, and means wherebythe bolt or plug may be moved in the opposite direction and allow thedies to move in, the projections of the inner ends of the dies thenentering within the groove or grooves of the bolt or plug.

In witness whereof I have hereunto signed my name this 4th day of August1916, in the presence of two subscribing witnesses.

HERBERT AUSTIN.

WVitnesses:

ERNEST HARKER, STEPHEN WATKINS.

Copies of this patent may be obtained for five cents each, by addressingthe Commissioner of Patents. Washington, I). G.

